- Legionnaires’ disease is a potentially fatal form of pneumonia.
- People may get infected when they breathe in tiny water droplets (aerosols) or droplet nuclei (particles left after the water has
evaporated) contaminated with elevated concentrations of Legionella bacteria.
- It is associated with stagnant water.
- Legionella bacteria grow best between temperatures of 20°C – 45°C with optimum growth temperature being 35°C – 40°C. High temperatures (minimum 60°C) kill the bacteria.
- Legionella bacteria are found in low numbers in natural aquatic environments, for instance, lakes, rivers and ground water. As a result it is virtually impossible to prevent Legionella bacteria entering man-made water systems.
- In low numbers the bacteria are generally considered harmless. With the correct conditions, e.g. warm water, the presence of micro-organisms and nutrients in the water or materials such as rust, the bacteria can grow and multiply to high levels which increase the risk of exposure. The bacteria tend to grow in biofilms (slime). Biofilms are likely to form on surfaces where there is low water flow or water is allowed to stagnate. However the growth of the bacteria can be controlled.
- The likelihood of contracting Legionnaires’ disease is related to:
- the level of contamination in the water source;
- the ability of the water source to generate aerosols and;
- the susceptibility of the person exposed to the contaminated water.
- Legionnaires disease is a potential biological hazard for cleaners. In general, anyone who encounters aerosols containing the bacteria may be susceptible to the disease but the risk is higher for males than females, if you are aged over 45, a smoker or if your immune system is impaired. Young people tend to be less susceptible to Legionnaires’ disease.
Symptoms of Legionnaires’ disease
- The symptoms of the disease are similar to those for flu with initially;
- high temperature
- muscle pains
- This may be followed by a dry cough and breathing difficulties leading eventually to pneumonia. In some cases there may be diarrhoea, vomiting and / or mental confusion.
- Symptoms usually develop 2 to 10 days after infection.
- In some cases infection can be fatal.
- The disease is not contagious and cannot be transferred from person to person.
Where may potential sources of aerosols containing Legionnaires Disease be encountered
The following is a non exhaustive list of potential sources of aerosols which may contain Legionella bacteria:
- Wet cooling systems for example, cooling towers and evaporative condensers;
- Spa pools e.g. Jacuzzis;
- Hot and cold water systems including showers, shower heads, eye washes and taps;
- Machine cooling systems for example, in lathes and plastic injection moulding machines;
- Spray booth water curtains;
- Humidifiers in food cabinets and factories;
- Ornamental fountains and water features;
- Dust suppression systems such as those used in cement and waste recycling industries;
- Horticultural misting systems, lawn sprinklers;
- Clinical humidifiers;
- Fire fighting systems for example, sprinklers and hose reels;
- Vehicle washes and power hoses.
- A water system includes all plant / equipment and components associated with that system, for instance, all associated pipe work, pumps, feed tanks, valves, shower heads, heat exchangers, quench tanks and chillers. When assessing a water system consider the whole system and not, for example, the cooling tower in isolation.
Legislation applicable to Legionnaires’ disease
Safety, Health and Welfare at Work Act 2005 (No. 10 of 2005)
- Under the Act, every employer must prepare a safety statement which is based on an identification of the hazards and an assessment of the risks to the Safety, Health and Welfare of his / her employees.
- In carrying out the risk assessment, consideration must be given to the risk of exposure to Legionella bacteria.
Where a risk is identified, the safety statement must specify the control measures in place to control or minimise the risk of exposure. The Act also requires those who have control to any extent of a place of work, for example, a management company which looks after water services, to carry out a risk assessment in relation to their duty to persons other than their employees.
- In doing so, they must consider the risk of exposure to Legionella bacteria.
- Also, under this legislation, whoever designs, manufactures, imports or supplies articles (which includes plant, machinery and appliances) for use at work, must so far as reasonably practicable:
- Ensure that the article is designed and constructed so that it will be safe and without risk to health when properly used at work;
- Provide or arrange for the provision of adequate information to the user about the article to ensure its safe use. This information should include details about the risk and the measures necessary to ensure that the article is operated and maintained correctly and safely.
Safety, Health and Welfare at Work (Biological Agents) Regulations 1994, as amended in 1998 (S.I. No. 146 of 1994 and S.I. 248 of 1998)
- Under these regulations, Legionella spp. are classified as Group 2 biological agents. This means that Legionella bacteria can cause human disease and might be a hazard to employees but it is unlikely to spread to the community and there is usually effective prophylaxis or treatment available.
The regulations set out the duties of employers to prevent exposure to a biological agent or, if complete prevention is not possible, to minimise exposure.
- The regulations build on the requirements of the Safety, Health and Welfare at Work Act 2005, to carry out a written assessment of the risk of exposure of any employee to a biological agent such as Legionella bacteria.
- The employer must also provide employees with information and training with respect to the risk posed
by biological agents such as Legionella bacteria.
The employer must carry out a written risk assessment. The level of risk assessment will depend upon the water system. Simple systems of very low risk may
only require a simple assessment whilst complex, high risk systems, for example, water systems incorporating cooling towers, will require a very detailed assessment. Ensure that the risk assessment
is carried out by a competent person and that employees are consulted during the risk assessment process.
In carrying out the assessment:
1. Identify potential sources of risk.
- Identify and assess sources of risk, for example, identify any systems which contain water likely to be >20°C and < 55°C which may release a spray of water droplets.
- Identify the source and quality of the system supply water, for instance whether or not from mains
- Identify any possible sources of contamination of the supply water within the premises.
- Look at physical conditions, for example, the design and condition of the water system.
- Identify any infrequently used water outlets such as infrequently used showers and taps.
2. Decide who might be harmed and how.
- Identify any particularly susceptible or sensitive groups of employees.
- Take account of other people who may be affected by your operations, for example, members of the public.
- Consider the duration and frequency of personal exposure to the aerosol, for example how often a person may be exposed and for how long.
- The employer must also ensure that employees have adequate information and where appropriate written instructions on work equipment which should address the normal conditions of use of the equipment and actions to identify and control foreseeable abnormal situations.
- Provide appropriate training and instructions to employees.
3. Evaluate the risks and decide on precautions.
- If a risk is identified consider whether or not the risk can be avoided, for example can a wet cooling system be substituted with a dry air cooling system.
- Eliminate stagnation in the water system – for example, where possible remove dead legs (sections of pipe leading to a fitting through which water only passes when there is a draw off from the fitting) and blind ends (pipe work that has been altered or capped such that water cannot flow through it).
- Control the release of water spray / aerosols, for example, use drift eliminators on cooling towers in order to limit aerosol dispersal.
- If the risks can be eliminated and the appropriate action is taken, then the assessment is complete but the assessment must still be regularly reviewed.
- If the risk cannot be eliminated then adequate control measures must be put in place.
- Appoint someone to manage the control measures. Ensure that roles and responsibilities are clearly defined, for instance for employees and contractors. Ensure that any service providers working are competent.
4. Record your findings and implement them.
- Record the results of the risk assessment. Cross reference any relevant health and safety documentation in the assessment.
- Document the written scheme for preventing or controlling the risk for example, what biocide concentration is being used, temperature measurements and the checks that are to be carried out.
- Document what remedial action is to be taken if controls fail.
- Describe the safe and correct operation of plant and equipment, prepare documented procedures.
- Keep an up to date schematic diagram of your systems. The diagram should show any dead legs, all system control valves, standby valves, water treatment plant, dosing points, drain valves and make up water supply.
- Retain any documentation and records. Records of operation and maintenance of the system should include when the plant and equipment has been or not been in operation, when parts have been isolated, results of any inspection, tests or remedial action. All test and inspection records must be kept for 5 years from the date of the inspection and be available for inspection by an Inspector from the Authority.
5. Review your risk assessment and update if necessary.
- Review your risk assessment at regular intervals and especially if significant changes are made for example, changes to plant and equipment design or operation, changes to the building or water treatment, if personnel change or if lack of control is evident.
- Consider if there is potential for water droplets to be dispersed over a wide area.
- Take account of the normal operation of equipment and also reasonably foreseeable conditions, for instance, equipment breakdowns.